If you're in cold or humid environments, the GoPro Anti-Fog Inserts will help ensure that everything remains fog free. All you have to do is drop one into the housing and it will prevent the fog from forming. You can use it up to four times just simply dry it out and store in an airtight bag. When you want to get the shot, you don't want fog to ruin it so make sure to have some of the GoPro Anti-Fog Inserts on hand.